cyand1317's blog

By cyand1317, history, 6 weeks ago, In English,

Hi, dear contestants!

With the end of Codeforces Round #431 (Div. 1 and Div. 2), some might be complaining behind the screen that problems are too tricky or hard, or have been struggling with some supposedly solvable problem... Yes, this time problems seem hard, but anyways, I hope they provided you with something, say rating, fun, ideas, or experience. I don't want to see anyone losing confidence because of failure (bad luck) in a single contest — please, don't do so.

Here are the hints, tutorials and codes for the problems. Feel free to discuss about problems in the comments, and point out if something is incorrect or unclear. Thank you!

849A - Odds and Ends

by cyand1317

Hint
Tutorial
Model solution

849B - Tell Your World

by cyand1317

Hint
Tutorial
Tommyr7's solution (first idea)
Model solution (second idea)

848A - From Y to Y

by cyand1317

Hint
Tutorial
Kalinin's solution
Model solution with knapsack (!)

848B - Rooter's Song

by cyand1317

Hint
Tutorial
Model solution

848C - Goodbye Souvenir

by adedalic

Hint
Tutorial
Model solution

848D - Shake It!

by cyand1317

Hint
Tutorial
Model solution

848E - Days of Floral Colours

by cyand1317

Hint
Tutorial
O(n^2) solution
Model solution

Behind the scene and random things (read if tired of problemsolving)

Expand

Thank you for reading. Next round? Perhaps something more traditional, who knows? Believe me, I'll try harder if this happens.

Cheers! \(^ ^)/


UPD Packages for problems are uploaded. They are in Polygon format and contain everything including statements, tests & generators, validators & checkers, and solutions. You can download them from Google Drive or Baidu Drive.

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By cyand1317, history, 7 weeks ago, In English,

Hi!

I’d like to invite you to Codeforces Round #431 which takes place at 16:35 MSK on 1 September. Please note that the timing is again unusual.

One of the problems is created by adedalic and KAN, while the others are authored by me. This is my second round here, and it couldn’t have been realized without efforts of: AlexFetisov, ifsmirnov, Tommyr7, winger and wu_qing who tested the problems; KAN who appears to be a meticulous guide throughout the preparation process; and MikeMirzayanov with the supercalifragilisticexpialidocious Codeforces and Polygon platforms — my deep gratitude to you!

Both divisions are welcomed as rated contestants and will have five problems to solve in two hours. The scoring will be announced later.

Once upon a time, in a virtual galaxy far, far away, there was a lovely young singer by the name of Hatsune Miku. One lovely day, Miku got a job as a vocalist in Vocaloid, and that was very exciting. People said, “Oh, Miku, you sing so accurately! And so emotive, too!” Soon everyone was talking about Miku, and there were songs and paintings and even lives for Miku. Miku liked that.

And you, are to start a journey following the emotions in Miku’s voice. Oh, by the way, a late Happy Birthday to her — August 31 is (was) her tenth anniversary.

See you then, and wish everyone few bugs and fair ratings.

UPD 1 Scoring will be:

  • 500-1000-1500-2000-2500 for Division 2;
  • 500-1000-1750-1750-2500 for Division 1.

UPD 2 System test is done. Congratulations to the winners!

Division 1

  1. dotorya
  2. Reyna
  3. SkyDec
  4. V--o_o--V
  5. koosaga

Division 2

  1. lmmortalCO (solved all problems!)
  2. ltg2030
  3. FoolMike
  4. HatsuneMiku
  5. MisakaKuma

Also, thanks to all who participated! Nicely done!

Check out the editorial with hints!

UPD 3 Complete tutorials and behind-the-scene fragments are out. Problem packages may be published soon, stay tuned!

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By cyand1317, history, 4 months ago, In English,

Greetings!

Codeforces Round #418 (Div. 2) has just come to an end. This is my first round here, and hope you all enjoyed the contest! > <

Seems the statements still created a few issues :( Anyway hope you liked it, and the characters feature the Monogatari anime series. Let me state again that the statements has little to do with the actual plot — they're inspired by five theme songs actually — and I'm not spoiling anyone of the series! ^ ^

Sympathy for those failing system tests on B... This problem was intended to experience a lot of hacks but somehow there are not so many.

Here are the detailed solutions to the problems. Feel free to write in the comments if there's anything incorrect or unclear.

Tutorial is loading...
Solution 1
Solution 2
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Solution 1
Solution 2 - Casework
Tutorial is loading...
Solution
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Solution 1 - DP on trees
Solution 2 - Greedy

One more thing — Staying up late is bad for health.

Tutorial is loading...
Solution 1 - O(n^5)
Solution 2 - O(n^3) by KAN

This is the round with the most solutions so far perhaps? There are at least 3 × 2 × 3 × 3 × 3 = 162 different ways to pass all problems in this round =D

Pla-tinum happy though I'm supposed to be
Pla-tinum sad is somehow how I get

Personally I'd like to express my gratitude to the community for creating this amazing first-time experience for me. Thank you, and see you next round. Probably it will be for Ha... Well, let's wait and see :)

Cheers \(^ ^)/

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By cyand1317, history, 4 months ago, In English,

418 I'm a teapot

Hi everyone! >///<

I'd like to invite you to Codeforces Round #418 which begins at 15:05 MSK on 7 June. Please note that the timing is unusual.

This is my first round here! KAN reviewed the contest and helped me through the preparation process, while Alladdin, neckbosov and Tommyr7 tested all the problems, and MikeMirzayanov and the awesome Codeforces and Polygon platforms made all this happen miraculously. This wouldn't have been possible without your efforts!

The round is rated for the second division, and participants from the first division can take part out of competition. As usual, there are five problems and two hours to solve them. The problems will feature... Well, let's wait and see :)

The scoring distribution will be announced later.

Hope everyone few bugs and fair ratings. Looking forward to seeing you then!

UPD 1 Scoring will be 500-1000-1750-1750-2500. It's recommended to read all problems' statements so as to find the problems that suit you — we tried quite hard to make them clear and interesting.

UPD 2 The round is delayed for 10 minutes due to technical issues. Apologies.

UPD 3 System test is done. Congratulations to the winners!

Div. 2 Top 5

  1. memanon
  2. marmoset
  3. liu_runda
  4. yieldar
  5. krydom

Overall Top 5

  1. xumingkuan
  2. HellKitsune
  3. natsugiri
  4. MakeYanGreatAgain
  5. irkstepanov

Hope you all enjoyed the contest. You all did a great job! The editorial is on the way, please be patient :)

UPD 4 For the impatient, here are the tutorials for problems A to C. More are coming!

UPD 5 The complete editorial is out. Cheers!

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